How B-29 crews trained to drop the bomb

Smith recalled that, upon arriving at Wendover, a civilian asked him to take a walk with him. "He said they wanted to build a fusing system for a new weapon. I asked if this were a biological or atomic weapon. For that I received a security investigation."

BEFORE 1944 WAS OUT, the Wendover squadrons had begun a rigorous training program. For the 509th, this meant frequent flights to practice dropping inert surrogates for Little Boy and Fat Man on targets limed on the desert floor. "We didn’t know what the bomb was," recalled Herman Stanley Zahn, one of the aircraft commanders. "All we were trying to do was drop it as accurately as we could." They also rehearsed an escape maneuver, which Tibbets had designed to get the airplane as far as possible from the expected blast. This was a kind of inside-out chandelle, beginning with a diving quarter roll from which the aircraft recovered 2,000 feet lower, and headed back the way it had come.

The 216th aircraft continued drop testing, led by Major Clyde Shields, who had piloted the Silverplate prototype. The flights were staged out of Wendover and Inyokern, California, near the Navy’s China Lake weapons proving ground. Drops were made on one range a few miles south of Wendover, and another at Sandy Beach, on California’s Salton Sea.

These missions were flown without a weaponeer, but with an electronics expert to monitor the dummy. Jeppson recalled occupying a small space behind the radio operator and next to the forward bomb bay. "We were just kind of there on a little platform," he said. "The monitoring box was hooked up to three coaxial cables into the bomb bay. We sat or kneeled."

It sounds simple enough, but Major Shields’ daily summaries compose a saga of frustration. Flights were thwarted by weather. Engines failed regularly, or went asthmatic in the thin air at bombing altitude. One engine fire largely consumed a B-29 on a Wendover runway. And then there was the incident over the little desert town of Calipatria, a few miles southeast of Salton Sea. "I was on that one," Jeppson recalled. "A Little Boy. I was monitoring my circuits, fusing, batteries, typical thing, flying at 30,000 feet." Suddenly the B-29 jerked upward. An engineer, who had gotten special clearance to be on the flight to observe how the Norden bombsight handled, had mistakenly released the bomb prematurely, wrote Gordon Thomas and Max Morgan Witts in Ruin from the Air: The Enola Gay’s Atomic Mission to Hiroshima. "It sailed over the town and landed in a farmer’s field," said Jeppson. The errant Little Boy buried itself so deep that security personnel simply filled in the hole. As for the mortified engineer, when the B-29 returned to Wendover, project agents escorted him to a car, drove him to Salt Lake City, and, after telling him he could no longer visit the base, put him on a train.

For training purposes, the inert dummies were filled with cement, carefully formulated to match the density of a high explosive called Composition B. Orange-painted bombs, called pumpkins, were stuffed with several tons of Composition B—making them the largest conventional bombs in the American arsenal.

In all, Wendover-based B-29s dropped about 155 Little Boy and Fat Man dummy bombs. The crews proved more resilient than the first generation airframes. Crews began shuttling to the Martin plant in Omaha and returning with brand-new bombers—the top of the Silverplate line. Pneumatically operated bomb bay doors flicked open and closed like aluminum eyelids. All were configured to carry Little Boy or Fat Man bombs in the forward bomb bay, with the option of carrying either conventional bombs or a 600-gallon auxiliary fuel tank in the aft bay. The Wright Cyclones had been replaced with fuel-injected engines and electrically operated reversible-pitch propellers, used to brake on landing and for maneuvering on the ground.

Jim Price and his crew flew the first new Silverplate to Wendover in April. Paul Tibbets, now a full colonel, is said to have selected his airplane as it moved down the Omaha assembly line. In Washington, D.C., Brigadier General Lauris Norstad, chief of staff of the 20th Air Force, set the stage for the 509th’s arrival in the Pacific theater. In a top-secret note to Curtis LeMay, then commanding XXI Bomber Command, Norstad explained that the 509th had been created to deliver special bombs. "[T]he first of these bombs will be available for delivery in August 1945. [They] are of two types, each weighing about 10,000 pounds. The power of each…is of the order of several thousand tons TNT equivalent.... In order to provide facsimiles of the more bulky type of special bomb, for use in training and rehearsal, the ‘Pumpkin’ has been developed….While originally designed for training…this bomb should have very definite tactical uses...in battle."

Tibbets went to Tinian in May. The full 509th complement followed on Green Hornet C-54s and by sea. In June, after a few weeks of further rehearsals with test units, 13 of the new Silverplates headed west, finally bound for combat. Curiously, no one from the 509th was around on July 16 to witness Trinity, the world’s first atomic blast, in the New Mexico desert.

Once on Tinian, the Silverplate B-29s began flying unescorted single-airplane missions to Japan, dropping the pumpkin bombs on industrial and military targets. The desired effect may have been more psychological than tactical, according to Stan Zahn. "The enemy became accustomed to single airplanes flying over," he said. And that big object falling earthward? Just another pumpkin.

About Carl A. Posey

Novelist and award-winning science writer Carl A. Posey was the author of seven published novels, a number of non-fiction books, and dozens of magazine articles. He was a licensed pilot and an Air & Space magazine contributor for more than 30 years, beginning with its second issue in 1986. Posey died on February 9, 2018.